Quickly opening & closing windows could result in an error allocating
the EGL context.
In my tests the window would be created but not display (in GNOME)
hanging for a while although Blender could be usable again after a
while. However some users report this crashing (see #123096).
Change the behavior to match X11, where failure to set the context
makes the GHOSTWindow::getValid return false.
In my tests the Blender window is created after a short delay.
This may also resolve#123096.
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